Saturday, May 31, 2014

The Radio Spectrum

The different users of the radio spectrum are called services, such as the broadcasting service or Amateur Radio Service. Each service gets a certain amount of spectrum to use, called a frequency allocation. Amateur Radio, or ham radio, has quite a number of allocations sprinkled throughout the radio spectrum.

Radio waves at different frequencies act differently in the way they travel and require different techniques to transmit and receive. Because waves of similar frequencies tend to have similar properties, the radio spectrum is divided
into four segments:

Shortwave or High-Frequency (HF): Frequencies below 30 MHz
Includes AM broadcasting, ten different ham radio bands, ship-to-shore
and ship-to-ship, military, and Citizens Band.

Very High Frequency (VHF): Frequencies from 30 to 300 MHz Includes
TV channels 2 through 13, FM broadcasting, three ham bands, public
safety and commercial mobile radio, and military.

Ultra High Frequency (UHF): Frequencies from 300 MHz to 1 GHz.
Includes TV channels 14 and higher, two ham bands, cellular phones,
public safety and commercial mobile radio, and military.

Microwave: Frequencies above 1 GHz. Includes GPS, digital wireless telephones,Wi-Fi wireless networking, microwave ovens, eight ham bands, satellite TV, and numerous public, private, and military users.

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